12x+7=21x^2

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Solution for 12x+7=21x^2 equation:


Simplifying
12x + 7 = 21x2

Reorder the terms:
7 + 12x = 21x2

Solving
7 + 12x = 21x2

Solving for variable 'x'.

Combine like terms: 21x2 + -21x2 = 0
7 + 12x + -21x2 = 0

Begin completing the square.  Divide all terms by
-21 the coefficient of the squared term: 

Divide each side by '-21'.
-0.3333333333 + -0.5714285714x + x2 = 0

Move the constant term to the right:

Add '0.3333333333' to each side of the equation.
-0.3333333333 + -0.5714285714x + 0.3333333333 + x2 = 0 + 0.3333333333

Reorder the terms:
-0.3333333333 + 0.3333333333 + -0.5714285714x + x2 = 0 + 0.3333333333

Combine like terms: -0.3333333333 + 0.3333333333 = 0.0000000000
0.0000000000 + -0.5714285714x + x2 = 0 + 0.3333333333
-0.5714285714x + x2 = 0 + 0.3333333333

Combine like terms: 0 + 0.3333333333 = 0.3333333333
-0.5714285714x + x2 = 0.3333333333

The x term is -0.5714285714x.  Take half its coefficient (-0.2857142857).
Square it (0.08163265305) and add it to both sides.

Add '0.08163265305' to each side of the equation.
-0.5714285714x + 0.08163265305 + x2 = 0.3333333333 + 0.08163265305

Reorder the terms:
0.08163265305 + -0.5714285714x + x2 = 0.3333333333 + 0.08163265305

Combine like terms: 0.3333333333 + 0.08163265305 = 0.41496598635
0.08163265305 + -0.5714285714x + x2 = 0.41496598635

Factor a perfect square on the left side:
(x + -0.2857142857)(x + -0.2857142857) = 0.41496598635

Calculate the square root of the right side: 0.644178536

Break this problem into two subproblems by setting 
(x + -0.2857142857) equal to 0.644178536 and -0.644178536.

Subproblem 1

x + -0.2857142857 = 0.644178536 Simplifying x + -0.2857142857 = 0.644178536 Reorder the terms: -0.2857142857 + x = 0.644178536 Solving -0.2857142857 + x = 0.644178536 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.2857142857' to each side of the equation. -0.2857142857 + 0.2857142857 + x = 0.644178536 + 0.2857142857 Combine like terms: -0.2857142857 + 0.2857142857 = 0.0000000000 0.0000000000 + x = 0.644178536 + 0.2857142857 x = 0.644178536 + 0.2857142857 Combine like terms: 0.644178536 + 0.2857142857 = 0.9298928217 x = 0.9298928217 Simplifying x = 0.9298928217

Subproblem 2

x + -0.2857142857 = -0.644178536 Simplifying x + -0.2857142857 = -0.644178536 Reorder the terms: -0.2857142857 + x = -0.644178536 Solving -0.2857142857 + x = -0.644178536 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '0.2857142857' to each side of the equation. -0.2857142857 + 0.2857142857 + x = -0.644178536 + 0.2857142857 Combine like terms: -0.2857142857 + 0.2857142857 = 0.0000000000 0.0000000000 + x = -0.644178536 + 0.2857142857 x = -0.644178536 + 0.2857142857 Combine like terms: -0.644178536 + 0.2857142857 = -0.3584642503 x = -0.3584642503 Simplifying x = -0.3584642503

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.9298928217, -0.3584642503}

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